Formula not giving correct output

I have a fomula field in row 67 and 68 .Row 67 calculates the average and row 68 calculates the improvement i.e. average(row 68)- last row inserted(row 67). The values for improvements are not showing correct value. C68 seems to give correct value but B68 and D68 is giving wrong value.

B68=4.8-4.5 =0.3 but it shows 0.4C68=14.9-15.1=-0.2D68=11.3-10.2=1.1 but it shows 1.0

I have a fomula field in row 67 and 68 .Row 67 calculates the average and row 68 calculates the improvement i.e. average(row 68)- last row inserted(row 67). The values for improvements are not showing correct value. C68 seems to give correct value but B68 and D68 is giving wrong value.

B68=4.8-4.5 =0.3 but it shows 0.4C68=14.9-15.1=-0.2D68=11.3-10.2=1.1 but it shows 1.0